I. Field of the Invention
This invention relates generally to membrane or diaphragm switches, and more specifically to an improved construction of such switches whereby the reliability of the resulting product is increased and the manufacturing cost is reduced.
II. Discussion of the Prior Art
Diaphragm or membrane switches are now widely used in conjunction with a variety of electrical and electronic appliances. Typically, these switches comprise a base layer having a pattern of conductive switch contacts disposed thereon and overlaying this base layer is a spacer layer which has a plurality of apertures which are aligned with the conductive elements on the base layer when the spacer layer is superimposed on the base layer. Atop the spacer layer is a further flexible plastic layer having a pattern of conductive switch contacts on the underside thereof, this conductive pattern also being aligned with the apertures in the spacer layer. This upper layer commonly has graphics on its exposed outer surface to identify particular switch positions. The application of finger force to a marked area on the graphics layer results in the upper flexible layer being deformed through the aperture in the spacer layer so a circuit path is completed between the two switch contacts. The memory properties of the plastic from which the upper flexible layer is fabricated allow the switch contacts to separate once the finger force is removed.
It has been the existing practice in the fabrication of membrane switches to adhesively bond the spacer layer to the lower substrate and then to likewise bond the upper metallized layer to the other major surface of the spacer member. Then, the graphics may be imprinted on the exposed surface of the upper flexible layer or, alternatively, a separate label layer may be adhesively bonded to the upper flexible layer.
The various steps of bonding one layer to the other increases the overall manufacturing cost of the membrane switch. I have conceived of a way of manufacturing a membrane switch whereby the overall manufacturing cost is reduced without an attendant reduction in the reliability or useful life of the resulting switch array.